Anas b. Malik reported that two persons sneezed in the presence of Messenger of Allah ﷺ. He (the Messenger of Allah) invoked mercy for one, and did not invoke for the other. The one for whom he had not prayed said: So and so sneezed and you said: May Allah have mercy upon you. I also sneezed but you did not utter these words for me. Thereupon he (the Holy Prophet) said: That person praised Allah, and you did not praise Allah.

حَدَّثَنِي مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ نُمَيْرٍ، حَدَّثَنَا حَفْصٌ، - وَهُوَ ابْنُ غِيَاثٍ - عَنْ سُلَيْمَانَ،
التَّيْمِيِّ عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ عَطَسَ عِنْدَ النَّبِيِّ ﷺ رَجُلاَنِ فَشَمَّتَ أَحَدَهُمَا
وَلَمْ يُشَمِّتِ الآخَرَ فَقَالَ الَّذِي لَمْ يُشَمِّتْهُ عَطَسَ فُلاَنٌ فَشَمَّتَّهُ وَعَطَسْتُ أَنَا فَلَمْ تُشَمِّتْنِي .
قَالَ
" إِنَّ هَذَا حَمِدَ اللَّهَ وَإِنَّكَ لَمْ تَحْمَدِ اللَّهَ " .